Slack / play in drivetrain after ring & pinion install

[Mikepol2]

So it's been a couple of weeks since installing 4.09's and it seems like there is a lot of slack in the drivetrain. Sounds like a metal on metal tap or bang when I'm puttering around at stop signs or putting the car in the garage. When the car was on jack stands for testing at installation, I put it into reverse and let out the clutch pretty fast, and heard a really loud bang as it engaged that scared the crap out of me. Letting the clutch out slow minimizes it. I just thought I hadn't noticed it before (and still am wondering the same thing). But in normal driving it seems like somewhere there is about an inch of play or slack. It doesn't really seem to be coming from the differential, and my gear guy said he set the backlash on the tight end of the range anyway, and that if the backlash isn't right you get whine or moan from the diff but it's quiet as a mouse. One thing I do remember is that I lost the matchmarking between the drive shaft and pinion flange when the diff was out of the car, and had to kind of guess when I reattached the driveshaft. But it didn't look like the end of the driveshaft had any features that would matter. Any ideas what the heck the noise could be, or do any other manual transmission owners with stock drivetrains notice a similar noise?

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[Lo Pony]

You sure all your driveshaft bolts are tight? Has happened to me playing around with shaft/flange and made a bang. Otherwise, there shouldn’t be that much slack in the gears unless they were set up too loose. Everything else should be unchanged.

 

[69mach1-395]

Maybe the gear lash is too large, not a good thing.

 

[1320INC]

Did you put in new pinion bearing? Sounds like it could be not enough preload on pinion bearings. If there is any noise prior to engagement then you are hearing the pinion teeth and the ring teeth smacking together.

 

[Mikepol2]

Did you put in new pinion bearing? Sounds like it could be not enough preload on pinion bearings. If there is any noise prior to engagement then you are hearing the pinion teeth and the ring teeth smacking together.

Yep new pinion bearing installed...backlash set on the tight end of the range.

 

[1320INC]

How many inch lbs did you set the on the new pinion bearing?

 

[Mikepol2]

How many inch lbs did you set the on the new pinion bearing?

That, I don't know. Would have to ask my gear guy who installed them but I felt pretty good about him, his wife is a Ford service tech and got him all the factory specs.

 

[1320INC]

The only reason I ask is because a lot of people do not know how to set the pinion depth or they don't have the right tools. you have to lie a lot of adapters to go from a inch pound torque wrench all the way up to three quarter inch drive for the pinion nut. Even if the backlash (which is the left and right setting of the differential in the housing) is correct it doesn't necessarily mean that the pinion depth is proper. so even if he set a tight backlash, a pinion gear depth that it not deep enough in the differential will have slop when the teeth engage/disenengage. I'm definitely not questioning your mechanics knowledge but it's very hard to have a tight backlash without any sort of whine, those two kind of go together. Tighter backlashes are typically set on drag cars because believe it or not that millimeter equals ET on the track, if you do not have any whine in your rear end on acceleration or deceleration then chances are your backlash is not set set tight. You combine that with an improper pinion gear depth and it would explain the noises you are hearing

 

[Mikepol2]

Hmm thanks for the info. Finding someone reputable to install gears has always been the most difficult thing when it comes to modding my cars. The X-factor is that other people on these forums complain about basically the same thing with un-modded differentials...my car sounds a lot like this guy's in the video in his original post, and interestingly, both of us first noticed with the car up on jackstands so there was no resistance in the drivetrain. My car also sounds like the subsequent poster who talks about the clacking in low speed over speed bumps.

https://www.mustang6g.com/forums/threads/opinions-on-drive-train-slack.118658/

 

[1320INC]

Every gear that meshes together from where the input shaft goes all the way back to the differential there's going to be a little bit of play in every one of those. so by the time you get to the rear end of the car all of that play is going to be exemplified. Maybe I misread your post it sounded like you were saying that your car makes these noises when you're driving it all of them are going to make noises up on jack stands that's totally normal

 

[Mikepol2]

Ah gotcha, no it's quiet as a mouse in normal driving. No bangs, taps, moans, whines, etc. It's only at low speeds (like pulling into the garage) that you can hear all the banging around. In fact there's what sounds like a separate "tap-tap-tap" when I shut off the engine with the car already in neutral, that sounds different from the clanking at low speed driving.

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